An honors student – egged on by pals to “subway surf” atop a train in Manhattan yesterday – was killed when his head struck a cement beam and he fell on the tracks and was run over, police said.

Eric Alvarez, 14, of Harlem was on his way home from Chelsea HS at about 4 p.m. when he accepted the dare to pull the deadly stunt on top of the second-to-last car on a moving C train, just south of the West 14th Street station at Eighth Avenue, police said.

The “extremely smart” Alvarez, who was such a computer whiz that he was taking special math classes after school at Stuyvesant HS, was killed instantly.

His mother, Tracy Askins, frantically rushed to the scene after one of her son’s friends phoned her with the horrific news. The heartbroken mom then collapsed at the West 14th Street station and was briefly hospitalized.

Reached at home last night, the mom choked back sobs, saying she couldn’t bear to talk about her son.

“I’m sorry. I can’t talk now. Not yet, not yet,” Askins whispered before breaking down again.

Another stricken aunt, Haydee Alvarez, noted that the family had just buried the teen’s great-grandmother last week.

“[Eric] was extremely smart – too smart for what happened to him,” Haydee Alvarez said. “I’m in extreme shock that he would even try something like that.”

Cops said witnesses told them the boy accepted the dare to exit the moving train through doors between cars just after it left the West 4th Street station and climb to the roof.

But the dead teen’s pals insist that Alvarez – a hard-working newspaper delivery boy, rabid Yankee fan and extremely computer-savvy student at Chelsea – died when he simply tried to move to a less crowded car and fell between cars.

One friend, 13, said that as Alvarez stood between cars, the train hit a bump, and “he hit his head on the wall.”

“We tried to hold his legs, but he fell. We saw blood on the train,” she said.

As the teen’s mangled body was being removed from the station, another girl cried, “My best friend fell to the track! I just lost my best friend!”

The boy’s cousin, Maria Gonzalez, said that if it’s true he was dared by pals into surfing, “I want these kids to know they lost a good friend.”